With development of the society and improvement of the material condition, various electronic devices such as cell phones, computers, TV and so on become popular in people's work and life. However, while the electronic devices provide convenience to the people, the issue of personal information leakage may arise. For example, taking display devices as known as examples, the known display devices typically have a large visible angle of view, which is a significant advantage for public display, but it is adverse to security of personal information.